I got this for my new Explore Scientific 127mm triplet, for imaging with my Canon 40D and 450D. (Mainly daytime terrestrial photography, of birds. I didn't expect this reducer to be perfect, since it's a one size fits all 800-1000mm and very hard to find reviews, but I was very pleasantly surprised. It provides 0.7934x reduction (even better than 0.8x, bringing my scope down to 755.7 mm @ f/5.95 it yields a tack sharp image, with no added aberrations that I can see. The corners in APS-C 22mm by 15mm format are nearly as sharp as the center (still pixel sharp, with a nearly rotationally symmetric point spread function, and the focal plane is *almost* flat using the Televue Wide T-Adapter. The curvature of the corrected focal plane is on the order of 1/16 turn of the fine-tuning knob (7.7:1 ratio, so about 1/120 turn of the coarse focusing knob — a tiny fraction of a millimeter of tube travel on the ES127's Crayford focuser to get the corners in focus after focusing on the center, which is very close to flat. The reducer (with TE-RAD-1074 ******* on adds almost exactly 60 mm of focus path length. On my ES127, this means that infinity focus is about 25 mm out with the reducer (it's about 85 mm out without it. To give myself the maximum terrestrial close focus, I might buy a 1 inch screw-on extension tube and use a 2 parfocalizing ring on it. I think with a negative spacers on the order of 1 mm or less I could get the focal plane flatness even more perfect, but that would require a thinner Wide T-Adapter (since there's no such thing as a negative spacer. Given that this was designed for a Televue scope, not Explore Scientific, I am impressed... and I expect that this reducer/corrector is going to be my workhorse for imaging with the ES127.